Spearfish Formation

On June 1st I was taken with this colorful bluff of the Belle Fourche [Beautiful Fork] River in Hulett, Wyoming. As far as I can tell, these rock layers are part of what geologists call the Spearfish Formation.

Is that the river in the first photo? It seems so narrow; perhaps that bit of green in the lower left is an island in the stream, rather than the opposite bank. I smiled at your remark about not being sure whether that geological formation was in Wyoming or South Dakota. When I got to the high plains of Kansas — especially the state lines between Kansas, Oklahoma, and Colorado, the arbitrariness of the divisions became clear. The land didn’t care.